Deciphering Quaternary Geomagnetic, Glacial, and Depositional Histories Using Paleomagnetism in Tandem with Other Chronostratigraphic and Sedimentological Approaches

• Main Author: Reilly, Brendan T.
• Other Authors: Stoner, Joseph S., Belart, Francisca, Mix, Alan C., Koppers, Anthony, Carlson, Anders, College of Earth, Ocean, and Atmospheric Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Paleomagnetism > Quaternary; Sediments (Geology); Geology; Stratigraphic > Quaternary; Marine sediments; Paleoclimatology > Quaternary; Greenland; Petermann Fjord; glacier; Ice Sheet; Petermann glacier; Sea ice
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/p5547x40v

Stratigraphy and chronology are essential to sedimentological study of Earth system histories. And, stratigraphy and chronology are often challenging and interesting problems themselves. The Quaternary (2.588 Ma - present) experienced paleoenvironmental and paleo-geomagnetic variability well outside the range of the recent instrumental record, providing the opportunity to place recent observations in a more complete perspective. This dissertation presents three studies that combine paleomagnetism in concert with radiocarbon, stratigraphic correlation, and/or age-depth modeling to develop stratigraphy and assign chronology. This in turn, helps to better understand the evolution of these glacial, geomagnetic, and depositional systems. The first study investigates the glacial history of the Petermann Glacier, a major outlet glacier of the Greenland Ice Sheet, over the last ~7 ka. Petermann Glacier has been remarkably stable for as long as there have been historical observations apart from two anomalously large calving events of its floating ice tongue over the last decade. This is unique when compared with many other large marine terminating Greenland outlet glaciers. Yet, our geologic evidence clearly show the Petermann Ice Tongue was not present for much of the time recorded in the sediments of Petermann Fjord. While radiocarbon and paleomagnetic methods could not constrain the sediment’s chronology alone, due to large reservoir issues and uncertain regional paleomagnetic templates, using the two methods in tandem we determine the paleoenvironmental conditions that were required to maintain the stable ice tongue of the Late Holocene. Specifically, a stable ice tongue only formed around 2-2.5 ka after sea ice conditions intensified, limiting Ekman transport of warm modified Atlantic Waters into the fjord, and surface air temperatures were within ~2o C of preindustrial conditions, slowing the subglacial run-off driven circulation of the fjord. The second study investigates the geomagnetic history of Western North ...